As for the argument of changes to "productivity". For starters very few of us work in roles where productivity is a directly measurable thing. Sure you can argue about commits, lines of code, ship times, but those are all nowhere near as measurable as "widgets-per-hour". On top of this we all know that a huge portion of roles out there are arguably not productive at all (and if they are it's very hard to measure). And again, when in the history of work has declining worker productivity been solved by improving conditions for the worker? If you company goes remote and you don't work as well that way, do you think your boss is going to go "oh! I'd better talk to leadership about getting those offices again!"?
The entire reason offices still exist is because of culture. For years every SV startup I knew said they needed an office in SF because the "VCs like to see that". There has been a lot of inertia towards offices.
Now that Covid19 has broken that assumption for a bit, I think we'll see a rapid shift to remote teams because it quickly becomes clear that offices are a liability. Anecdotally I already know one start up that can no longer afford their office and so are breaking their lease with no sense of what they'll do next (so remote is the default), and a well established, very traditional office culture firm that is already stating that everyone being in the office full time will not be the norm coming out of this.